高效液相色谱法测定婴幼儿配方奶粉中酪蛋白磷酸肽含量

目的建立高效液相色谱法(highperformanceliquidchromatography,HPLC)测定婴幼儿配方奶粉中酪蛋白磷酸肽(casein phosphopeptide, CPP)的含量的方法。方法对样品静置温度、静置时间、沉淀分离方式进行优化,用高效液相色谱法对婴幼儿配方奶粉中CPP的含量进行测定。结果最优的前处理条件为样品溶解后调整pH至4.6,于4℃条件下静置1 h,过滤后上清液经0.22μm滤膜过滤,以Ultimate AQ-C_(18)色谱柱(250mm×4.6mm,5μm)分离。经钼蓝比色法鉴定,保留时间为8.387min的组分为CPP。该方法在10～1000mg/L范围内线性关系良好,相关系数为0.9993,定量限为4.40 mg/L,婴幼儿奶粉中添加量为500、1000、5000 mg/kg时, CPP的回收率为96.63%%～101.42%。结论该方法样品前处理简单,稳定性和可靠性良好,检测结果符合定性定量要求,可用于婴幼儿配方奶粉中CPP含量的测定。     

Effective water splitting using N-doped TiO2 films: Role of preferred orientation on hydrogen production

N-doped TiO₂ film with preferred (211) orientation, deposited by RF magnetron sputtering, was investigated for the water-splitting hydrogen production. It is found that the preferred crystal growth orientation of the films can be controlled by N₂ flow rate during the deposition. The results reveal that not only the N-doping, but also the preferred orientation (i.e., large percentage of exposed (211) facet), can effectively enhance the activity of TiO₂-based photocatalyst. With the increase of exposed (211) facets, the hydrogen production rates of N-doped TiO₂ films rise from 760 μmol H₂ h⁻¹ m⁻² to 4500 μmol H₂ h⁻¹ m⁻², indicating that high performance of TiO₂-based photocatalyst can be achieved by controlling the preferred orientation of the films.     

橙汁中的条件致病酵母菌及其控制策略

橙汁中普遍存在酵母菌,其中部分对人体是无害的。但是近年来的研究发现,一些酵母菌的存在不但会引起橙汁腐败,还会导致人体感染患病。酵母菌是橙汁中最常见的条件致病菌之一,随着人们对橙汁饮用安全和人体健康潜在威胁的深入认识,条件致病酵母菌日趋受到重视。对致病酵母菌的研究也成为生命科学研究的热点。目前已知的橙汁酵母致病菌有14种：近平滑假丝酵母(Candida parapsilosis)、星形假丝酵母(C.stellata)、热带假丝酵母(C.tropicalis)、无名假丝酵母(C. famata)、小丘假丝酵母(C. colliculosa)、涎沫假丝酵母(C. zeylanoides)、葡萄牙棒孢酵母(Clavispora lusitaniae)、新型隐球酵母(Cryptococcus neoformans)、汉逊德巴利酵母(Debaryomyces hansenii)、葡萄汁有孢汉逊酵母(Hanseniaspora uvarum)、东方伊萨酵母(Issatchenkia orientalis)、异常汉逊酵母(Pichia anomala)、粘质红酵母(Rhodotorula mucilaginosa)、阿萨希丝孢酵母(Trichosporon asahii)。本文对这些橙汁中条件致病酵母菌的种类、鉴定方法及其控制策略进行了系统地的综述与评述,为橙汁生产、储藏、销售和消费提供参考。     

多糖的磷酸化修饰及其生物活性研究进展

多糖是由多个单糖分子经脱水缩合,藉由糖苷键连接而成的天然大分子化合物,在生物中有储存能量、信息传递和组成结构的作用。多糖的理化性质受其空间结构、分子量、侧链取代基类型、数量和位置的影响。选择合适的改性方法对多糖进行分子修饰,提高其生物活性,这是研究多糖构效关系及开发多糖产品的重要途径。磷酸化多糖是多糖经特定的化学方法进行磷酸基团结构修饰制备的衍生物。本文重点阐述了酸法、磷酰氯法和磷酸盐法3种磷酸化多糖的修饰工艺和工艺条件,分析目前存在的问题,归纳了磷酸化多糖在抗氧化、抗肿瘤、抗病毒和免疫调节等方面的生物活性作用,旨在为多糖的构效研究中提供工艺参考和理论依据。     

传统加热酸溶性钛渣实验研究

以酸溶性钛渣为原料,对其进行传统加热氧化焙烧实验研究。考察了焙烧温度及保温时间对样品中二氧化钛、硫、碳含量的影响。结果表明：随着焙烧温度升高,氧化焙烧过程中低价钛、铁以及氧化亚铁的氧化使物料总量增加,而钛总量不变,导致焙烧后物料中二氧化钛含量随着焙烧温度的升高而降低;随着保温时间增加,各成分的氧化反应进行得更彻底,物料中二氧化钛的含量不断降低;随着焙烧温度的升高及保温时间的增加,碳与硫的脱除效果明显,其含量不断降低。     

Economic production of probiotics from kitchen waste

In the present work, a novel treatment method of kitchen waste for economic production of probiotics was investigated. This required the selection of suitable probiotic microorganisms. Based on the pure cultures of probiotic strains for the fermentation kitchen waste, 5 strains of microorganisms including 1 strain of Lactobacillus, 2 strains of Bacillus, and 2 strains of yeast were selected, respectively. These probiotic microorganisms were mixed at the same ratio and cultured using the kitchen waste as culture medium at pH of 7.2 and temperature of 37°C. After 24 h, the total count of the viable cells reached 2.24 ×10¹⁰ CFU/g, which was higher than that obtained in any single probiotic strain pure culture. It was found that the presence of yeasts and Bacillus species enhanced the growth of Lactobacillus strain. Bench scale experiments were also done in a self-designed rotating drum type bioreactor. The experimental results indicate that there is a good possibility of utilizing kitchen waste for the economic production of probiotics.     

Improved bounds on partial derivatives of rational triangular Bézier surfaces

This paper applies inequality skill, degree elevation of triangular Bézier surfaces and difference operators to deduce the bounds on first and second partial derivatives of rational triangular Bézier surfaces. Further more, we prove that the new bounds are tighter and more effective than the known ones. All the results are obviously helpful for further optimization of geometric design systems.